CARMA1基因在活化B细胞样亚型弥漫大B细胞淋巴瘤中的研究进展

弥漫大B细胞淋巴瘤(DLBCL)为常见的侵袭性淋巴瘤,其中活化B细胞样(ABC)亚型DLBCL患者复发率高、生存率低,预后差.核因子(NF)-κB信号通路持续过度活化,是区分ABC亚型DLBCL与其他亚型DLBCL的显著特征之一,亦为导致ABC亚型DLBCL疾病发生的关键信号通路.近年,多项研究结果证实CARMA1通过调控NF-κB信号通路,进而在ABC亚型DLBCL疾病发生中发挥重要作用.笔者拟就CARMA1功能、基因点突变及翻译后修饰等方面对ABC亚型DLBCL疾病发生的影响进行综述.     

Critical roles of Pten in B cell homeostasis and immunoglobulin class switch recombination

Pten is a tumor suppressor gene mutated in human cancers. We used the Cre-loxP system to generate a B cell-specific mutation of Pten in mice (bPten(flox/flox)mice). bPten(flox/flox) mice showed elevated numbers of B1a cells and increased serum autoantibodies. Among B2 cells in bPten(flox/flox) spleens, numbers of marginal zone B (MZB) cells were significantly increased while those of follicular B (FOB) cells were correspondingly decreased. Pten-deficient B cells hyperproliferated, were resistant to apoptotic stimuli, and showed enhanced migration. The survival kinase PKB/Akt was highly activated in Pten-deficient splenic B cells. In addition, immunoglobulin class switch recombination was defective and induction of activation-induced cytidine deaminase (AID) was impaired. Thus, Pten plays a role in developmental fate determination of B cells and is an indispensable regulator of B cell homeostasis.     

Cernunnos influences human immunoglobulin class switch recombination and may be associated with B cell lymphomagenesis

Cernunnos is involved in the nonhomologous end-joining (NHEJ) process during DNA double-strand break (DSB) repair. Here, we studied immunoglobulin (Ig) class switch recombination (CSR), a physiological process which relies on proper repair of the DSBs, in B cells from Cernunnos-deficient patients. The pattern of in vivo generated CSR junctions is altered in these cells, with unusually long microhomologies and a lack of direct end-joining. The CSR junctions from Cernunnos-deficient patients largely resemble those from patients lacking DNA ligase IV, Artemis, or ATM, suggesting that these factors are involved in the same end-joining pathway during CSR. By screening 269 mature B cell lymphoma biopsies, we also identified a somatic missense Cernunnos mutation in a diffuse large B cell lymphoma sample. This mutation has a dominant-negative effect on joining of a subset of DNA ends in an in vitro NHEJ assay. Translocations involving both Ig heavy chain loci and clonal-like, dynamic IgA switching activities were observed in this tumor. Collectively, our results suggest a link between defects in the Cernunnos-dependent NHEJ pathway and aberrant CSR or switch translocations during the development of B cell malignancies.     

弥漫大B细胞淋巴瘤的治疗进展

弥漫大B细胞淋巴瘤是非霍奇金淋巴瘤中最常见的一种类型,也是发生在成人淋巴瘤中最常见的一种类型。其在临床表现、形态学、免疫表型、细胞遗传学、分子生物学、对化疗的反应及预后上都表现出明显的异质性。随着诊断医学的发展和新的药物的开发和应用,弥漫大B细胞淋巴瘤在诊断和治疗方面取得一些进展,特别是在免疫组化的分类和嵌合抗CD20单克隆抗体利妥昔单抗联合治疗方面,使弥漫大B细胞淋巴瘤在疗效和预后得到了很大的改善。     

弥漫性大B细胞淋巴瘤的临床病理研究进展

弥漫性大B细胞淋N（diffuselargeBcelllymphoma,DLBCL）是最常见的淋巴造血系统肿瘤。由于DLBCL表现出明显的异质性,所以对于它确切的分子机制还不是十分清楚。本文将对DLBCL的临床病理特点进行综述。     

弥漫性大B细胞性非霍奇金淋巴瘤利妥昔单克隆抗体联合化疗后免疫球蛋白的变化

利妥昔(rituximab,RTX)单克隆抗体能够迅速减少循环血液中B细胞的数量,导致血液免疫球蛋白减少。有关RTX引起的低免疫球蛋白血症也一直缺乏系统研究,为此我们研究了RTX联合CHOP方案治疗B细胞淋巴瘤血免疫球蛋白水平的变化。2004年1月至2009年12月我院收治的采用CHOP和R-CHOP治疗的18岁以上成年人初治CD20阳性弥漫性大B细胞非霍奇金淋巴瘤共122例,根据治疗方案的不同分为CHOP和R-CHOP两个组,记录两组病人各阶段免疫球蛋白水平的变化,剔除治疗前免疫球蛋白水平异常的病例后进行分析。结果显示,6个疗程结束后R-CHOP组82例基线免疫球蛋白正常的病人中,IgG水平比基线值下降超过20%的病人,占85.4%,低于正常值下限者占47.6%;IgA水平较基线值下降超过20%的病人同样占85.4%,低于正常值下限者占48.8%;IgM水平较基线值下降超过20%的病人占87.8%,低于正常值下限者占52.4%。CHOP组共24例治疗前后免疫球蛋白水平无显著变化。结论 :低免疫球蛋白血症是RTX联合CHOP方案化疗的常见并发症,免疫球蛋白血症水平多在停止治疗1年左右恢复至正常水平,少数病人免疫球蛋白的减少甚至可以持续2年以上。     

B cell receptor-independent stimuli trigger immunoglobulin (Ig) class switch recombination and production of IgG autoantibodies by anergic self-reactive B cells

In both humans and animals, immunoglobulin (Ig)G autoantibodies are less frequent but more pathogenic than IgM autoantibodies, suggesting that controls over Ig isotype switching are required to reinforce B cell self-tolerance. We have used gene targeting to produce mice in which hen egg lysozyme (HEL)-specific B cells can switch to all Ig isotypes (SWHEL mice). When crossed with soluble HEL transgenic (Tg) mice, self-reactive SWHEL B cells became anergic. However, in contrast to anergic B cells from the original nonswitching anti-HEL x soluble HEL double Tg model, self-reactive SWHEL B cells also displayed an immature phenotype, reduced lifespan, and exclusion from the splenic follicle. These differences were not related to their ability to Ig class switch, but instead to competition with non-HEL-binding B cells generated by VH gene replacement in SWHEL mice. When activated in vitro with B cell receptor (BCR)-independent stimuli such as anti-CD40 monoclonal antibody plus interleukin 4 or lipopolysaccharide (LPS), anergic SWHEL double Tg B cells proliferated and produced IgG anti-HEL antibodies as efficiently as naive HEL-binding B cells from SWHEL Ig Tg mice. These results demonstrate that no intrinsic constraints to isotype switching exist in anergic self-reactive B cells. Instead, production of IgG autoantibodies is prevented by separate controls that reduce the likelihood of anergic B cells encountering BCR-independent stimuli. That bacteria-derived LPS could circumvent these controls may explain the well-known association between autoantibody-mediated diseases and episodes of systemic infection.     

Pharmacoproteomics identifies combinatorial therapy targets for diffuse large B cell lymphoma

Rationally designed combinations of targeted therapies for refractory cancers, such as activated B cell–like diffuse large B cell lymphoma (ABC DLBCL), are likely required to achieve potent, durable responses. Here, we used a pharmacoproteomics approach to map the interactome of a tumor-enriched isoform of HSP90 (teHSP90). Specifically, we chemically precipitated teHSP90-client complexes from DLBCL cell lines with the small molecule PU-H71 and found that components of the proximal B cell receptor (BCR) signalosome were enriched within teHSP90 complexes. Functional assays revealed that teHSP90 facilitates BCR signaling dynamics by enabling phosphorylation of key BCR signalosome components, including the kinases SYK and BTK. Consequently, treatment of BCR-dependent ABC DLBCL cells with PU-H71 attenuated BCR signaling, calcium flux, and NF-κB signaling, ultimately leading to growth arrest. Combined exposure of ABC DLBCL cell lines to PU-H71 and ibrutinib, a BCR pathway inhibitor, more potently suppressed BCR signaling than either drug alone. Correspondingly, PU-H71 combined with ibrutinib induced synergistic killing of lymphoma cell lines, primary human lymphoma specimens ex vivo, and lymphoma xenografts in vivo, without notable toxicity. Together, our results demonstrate that a pharmacoproteome-driven rational combination therapy has potential to provide more potent BCR-directed therapy for ABC DLCBL patients.     

Ophthalmoplegia with diffuse large B cell lymphoma: vital differential diagnosis

Ophthalmoplegia is an unusual finding in diffuse large B cell lymphoma. This report describes the case of a 72-year old male patient who presented with ophthalmoplegia but no gross neurological manifestations and an isolated mass in the left upper thigh. His ophthalmoplegia improved from his first cycle of systemic and intrathecal chemotherapy, his thigh mass effusion spontaneously resolved, and his laboratory tests also showed improvement. The patient remained well, though weak, for several months with no other neurological signs. He subsequently died from clinically diagnosed pulmonary embolism.     

Epigenetic tethering of AID to the donor switch region during immunoglobulin class switch recombination

Immunoglobulin class switch recombination (CSR) is initiated by double-stranded DNA breaks (DSBs) in switch regions triggered by activation-induced cytidine deaminase (AID). Although CSR correlates with epigenetic modifications at the IgH locus, the relationship between these modifications and AID remains unknown. In this study, we show that during CSR, AID forms a complex with KAP1 (KRAB domain-associated protein 1) and HP1 (heterochromatin protein 1) that is tethered to the donor switch region (Sμ) bearing H3K9me3 (trimethylated histone H3 at lysine 9) in vivo. Furthermore, in vivo disruption of this complex results in impaired AID recruitment to Sμ, inefficient DSB formation, and a concomitant defect in CSR but not in somatic hypermutation. We propose that KAP1 and HP1 tether AID to H3K9me3 residues at the donor switch region, thus providing a mechanism linking AID to epigenetic modifications during CSR.     

Ki-67在弥漫大B细胞淋巴瘤中的表达及意义

目的：通过观察Ki-67在弥漫大B细胞淋巴瘤（DLBCL）与淋巴结反应性增生中以及在生发中心B细胞（GCB）型和非GCB型（non-GCB）中的表达差异,探讨Ki-67的临床意义。方法将60例DLBCL标本设为观察组,将20例淋巴结反应性增生组织标本设为对照组。比较Ki-67在GCB型和non-GCB型中的表达差异,并分析Ki-67与DLBCL分型、国际预后指数（IPI）、近期疗效、预后的关系。结果 Ki-67在观察组和对照组的平均表达率分别为（69．17±14．73）％和（40．50±14．95）％,差异有统计学意义（t＝7．509,P＜0．0001）。Ki-67在GCB型和non-GCB中的平均表达率分别为（59．29±14．92）％和（71．96±13．39）％,有显著差异（t＝3．019,P＝0．0038）。Ki-67在IPI＜2组和IPI≥2组中的平均表达率分别为（65．29±15．17）％和（74．23±12．70）％,差别有统计学意义（t＝2．422,P＝0．0186）。结论 Ki-67的异常表达与DLBCL的临床分期、IPI指数、分型、近期疗效及预后等相关,对判断疗效和预后具有重要临床价值。     

Role for DNA repair factor XRCC4 in immunoglobulin class switch recombination

V(D)J recombination and immunoglobulin class switch recombination (CSR) are two somatic rearrangement mechanisms that proceed through the introduction of double-strand breaks (DSBs) in DNA. Although the DNA repair factor XRCC4 is essential for the resolution of DNA DSB during V(D)J recombination, its role in CSR has not been established. To bypass the embryonic lethality of XRCC4 deletion in mice, we developed a conditional XRCC4 knockout (KO) using LoxP-flanked XRCC4 cDNA lentiviral transgenesis. B lymphocyte restricted deletion of XRCC4 in these mice lead to an average two-fold reduction in CSR in vivo and in vitro. Our results connect XRCC4 and the nonhomologous end joining DNA repair pathway to CSR while reflecting the possible use of an alternative pathway in the repair of CSR DSB in the absence of XRCC4. In addition, this new conditional KO approach should be useful in studying other lethal mutations in mice.